Researchers at National Taiwan University have made significant strides in understanding the selective conversion of carbon dioxide (CO2) into formate using copper chalcogenides. In a study published on December 3, 2025, in the journal Nature Communications, the team identified a charge-redistribution mechanism that illuminates the unique properties of these materials, long a subject of scientific intrigue.
For years, the capability of copper chalcogenides to convert CO2 into formate with remarkable selectivity has puzzled scientists. This selectivity is typically associated with p-block metals like tin or bismuth, rather than transition metals such as copper (Cu), which usually lacks such intrinsic product selectivity. Despite extensive research, the underlying reasons for this unusual behavior remained unclear until now.
Using advanced operando synchrotron-based X-ray spectroscopic techniques, the research team captured direct spectroscopic evidence that clarifies how these materials function. The findings reveal that chalcogenide anions play a critical role in stabilizing the catalytic structure. This stabilization prevents the over-reduction of cuprous (Cu+) species to metallic copper (Cu0), thus maintaining an electronic configuration conducive to the formation of mono-carbon intermediates, including both carbon monoxide (CO) and formate.
Moreover, the study highlights a dynamic charge-redistribution process that occurs within the Cu+ sites. This process stabilizes O-bound formate intermediates, guiding the reduction pathway of CO2 predominantly towards formate formation. As a result, the copper chalcogenide catalysts are able to effectively suppress competing pathways leading to CO and multi-carbon products, achieving near-complete selectivity for formate.
The research identified CuS as the optimal catalyst, achieving an impressive 90% faradaic efficiency for formate production at a voltage of −0.6 V. With a partial current exceeding an ampere scale, this catalyst demonstrates considerable potential for scalability in industrial applications.
Hao Ming Chen, a distinguished professor of chemistry at National Taiwan University and co-corresponding author of the study, noted the importance of this research. He stated, “Copper chalcogenides have fascinated researchers for decades because of their enhanced formate selectivity, but the true origin of this behavior was never fully understood. Our study reveals that charge-redistribution dynamics redefine the fundamental principles governing CO2 reduction selectivity and offer a new design strategy for tuning catalyst electronic structure via chalcogen modification.”
This research marks a significant advancement in the field of electrocatalysis. It not only provides fundamental insights into the mechanisms behind CO2 conversion but also sets the stage for future innovations in the design of catalysts for sustainable energy solutions.
By unraveling the complexities of copper chalcogenides, scientists are one step closer to enhancing the efficiency of CO2 reduction processes, contributing to the broader goals of environmental sustainability and energy transition. This work could pave the way for new technologies aimed at reducing carbon emissions and promoting cleaner energy sources.
